Microbicidal composition

ABSTRACT

Synergistic microbicidal compositions containing N-methyl-1,2-benzisothiazolin-3-one.

This invention relates to a synergistic combination of selected microbicides having greater activity than would be observed for the individual microbicides.

In some cases, commercial microbicides cannot provide effective control of microorganisms, even at high use concentrations, due to weak activity against certain types of microorganisms, e.g., those resistant to some microbicides, or due to aggressive environmental conditions. Combinations of different microbicides are sometimes used to provide overall control of microorganisms in a particular end use environment. For example, U.S. Pat. App. Pub. No. 2007/0078118 discloses synergistic combinations of N-methyl-1,2-benzisothiazolin-3-one (MBIT) with other biocides. However, there is a need for additional combinations of microbicides having enhanced activity against various strains of microorganisms to provide effective control of the microorganisms. Moreover, there is a need for combinations containing lower levels of individual microbicides for environmental and economic benefit. The problem addressed by this invention is to provide such additional combinations of microbicides.

STATEMENT OF THE INVENTION

The present invention is directed to a microbicidal composition comprising: (a) N-methyl-1,2-benzisothiazolin-3-one; and (b) at least one microbicide selected from among 2,2-dibromo-3-nitrilopropionamide, formaldehyde, 2-N-octyl-4-isothiazolin-3-one, propiconazole, tebuconazole, and a mixture of chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the following terms have the designated definitions, unless the context clearly indicates otherwise. “MBIT” is N-methyl-1,2-benzisothiazolin-3-one. The term “microbicide” refers to a compound capable of killing, inhibiting the growth of or controlling the growth of microorganisms at a locus; microbicides include bactericides, fungicides and algaecides. The term “microorganism” includes, for example, fungi (such as yeast and mold), bacteria and algae. The term “locus” refers to an industrial system or product subject to contamination by microorganisms. The following abbreviations are used throughout the specification: ppm=parts per million by weight (weight/weight), mL=milliliter, ATCC=American Type Culture Collection, MBC=minimum biocidal concentration, and MIC=minimum inhibitory concentration. Unless otherwise specified, temperatures are in degrees centigrade (° C.), and references to percentages (%) are by weight. Amounts of organic microbicides are given on an active ingredient basis in ppm (w/w).

The compositions of the present invention unexpectedly have been found to provide enhanced microbicidal efficacy at a combined active ingredient level lower than that of the individual microbicides.

In one embodiment of the invention, the antimicrobial composition comprises N-methyl-1,2-benzisothiazolin-3-one and 2,2-dibromo-3-nitrilopropionamide. Preferably, a weight ratio of 2,2-dibromo-3-nitrilopropionamide to N-methyl-1,2-benzisothiazolin-3-one is from 1:0.01 to 1:114, more preferably from 1:0.01 to 1:29, more preferably from 0.02 to 1:5.8.

In one embodiment of the invention, the antimicrobial composition comprises N-methyl-1,2-benzisothiazolin-3-one and formaldehyde. Preferably, a weight ratio of formaldehyde to N-methyl-1,2-benzisothiazolin-3-one is from 1:0.0022 to 1:19, more preferably from 1:0.022 to 1:19, more preferably from 1:0.17 to 1:19.

In one embodiment of the invention, the antimicrobial composition comprises N-methyl-1,2-benzisothiazolin-3-one and 2-N-octyl-4-isothiazolin-3-one. Preferably, a weight ratio of 2-N-octyl-4-isothiazolin-3-one to N-methyl-1,2-benzisothiazolin-3-one is from 1:0.02 to 1:882, more preferably from 1:0.13 to 1:882, more preferably from 1:0.13 to 1:150.

In one embodiment of the invention, the antimicrobial composition comprises N-methyl-1,2-benzisothiazolin-3-one and propiconazole. Preferably, a weight ratio of propiconazole to N-methyl-1,2-benzisothiazolin-3-one is from 1:0.0022 to 1:6.8, more preferably from 1:0.075 to 1:6.8.

In one embodiment of the invention, the antimicrobial composition comprises N-methyl-1,2-benzisothiazolin-3-one and tebuconazole. Preferably, a weight ratio of tebuconazole to N-methyl-1,2-benzisothiazolin-3-one is from 1:0.0033 to 1:46, more preferably from 1:0.15 to 1:46.

In one embodiment of the invention, the antimicrobial composition comprises N-methyl-1,2-benzisothiazolin-3-one and a 3:1 mixture of chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one. Preferably, the mixture is about a 3:1 mixture, respectively. Preferably, a weight ratio of the mixture to N-methyl-1,2-benzisothiazolin-3-one is from 1:91 to 1:114.

The microbicides in the composition of this invention may be used “as is” or may first be formulated with a solvent or a solid carrier. Suitable solvents include, for example, water; glycols, such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol; glycol ethers; alcohols, such as methanol, ethanol, propanol, phenethyl alcohol and phenoxypropanol; ketones, such as acetone and methyl ethyl ketone; esters, such as ethyl acetate, butyl acetate, triacetyl citrate, and glycerol triacetate; carbonates, such as propylene carbonate and dimethyl carbonate; and mixtures thereof. It is preferred that the solvent is selected from water, glycols, glycol ethers, esters and mixtures thereof. Suitable solid carriers include, for example, cyclodextrin, silicas, diatomaceous earth, waxes, cellulosic materials, alkali and alkaline earth (e.g., sodium, magnesium, potassium) metal salts (e.g., chloride, nitrate, bromide, sulfate) and charcoal.

When a microbicide component is formulated in a solvent, the formulation may optionally contain surfactants. When such formulations contain surfactants, they are generally in the form of emulsive concentrates, emulsions, microemulsive concentrates, or microemulsions. Emulsive concentrates form emulsions upon the addition of a sufficient amount of water. Microemulsive concentrates form microemulsions upon the addition of a sufficient amount of water. Such emulsive and microemulsive concentrates are generally well known in the art; it is preferred that such formulations are free of surfactants. U.S. Pat. No. 5,444,078 may be consulted for further general and specific details on the preparation of various microemulsions and microemulsive concentrates.

A microbicide component also can be formulated in the form of a dispersion. The solvent component of the dispersion can be an organic solvent or water, preferably water. Such dispersions can contain adjuvants, for example, co-solvents, thickeners, anti-freeze agents, dispersants, fillers, pigments, surfactants, biodispersants, sulfosuccinates, terpenes, furanones, polycations, stabilizers, scale inhibitors and anti-corrosion additives.

When both microbicides are each first formulated with a solvent, the solvent used for the first microbicide may be the same as or different from the solvent used to formulate the other commercial microbicide, although water is preferred for most industrial biocide applications. It is preferred that the two solvents are miscible.

Those skilled in the art will recognize that the microbicide components of the present invention may be added to a locus sequentially, simultaneously, or may be combined before being added to the locus. It is preferred that the first microbicide and the second microbicide component be added to a locus simultaneously or sequentially. When the microbicides are added simultaneously or sequentially, each individual component may contain adjuvants, such as, for example, solvent, thickeners, anti-freeze agents, colorants, sequestrants (such as ethylenediamine-tetraacetic acid, ethylenediaminedisuccinic acid, iminodisuccinic acid and salts thereof), dispersants, surfactants, biodispersants, sulfosuccinates, terpenes, furanones, polycations, stabilizers, scale inhibitors and anti-corrosion additives.

The microbicidal compositions of the present invention can be used to inhibit the growth of microorganisms or higher forms of aquatic life (such as protozoans, invertebrates, bryozoans, dinoflagellates, crustaceans, mollusks, etc.) by introducing a microbicidally effective amount of the compositions onto, into, or at a locus subject to microbial attack. Suitable loci include, for example: industrial process water; electrocoat deposition systems; cooling towers; air washers; gas scrubbers; mineral slurries; wastewater treatment; ornamental fountains; reverse osmosis filtration; ultrafiltration; ballast water; evaporative condensers; heat exchangers; pulp and paper processing fluids and additives; starch; plastics; emulsions; dispersions; paints; latices; coatings, such as varnishes; construction products, such as mastics, caulks, and sealants; construction adhesives, such as ceramic adhesives, carpet backing adhesives, and laminating adhesives; industrial or consumer adhesives; photographic chemicals; printing fluids; household products, such as bathroom and kitchen cleaners; cosmetics; toiletries; shampoos; soaps; detergents; industrial cleaners; floor polishes; laundry rinse water; metalworking fluids; conveyor lubricants; hydraulic fluids; leather and leather products; textiles; textile products; wood and wood products, such as plywood, chipboard, wallboard, flakeboard, laminated beams, oriented strandboard, hardboard, and particleboard; petroleum processing fluids; fuel; oilfield fluids, such as injection water, fracture fluids, and drilling muds; agriculture adjuvant preservation; surfactant preservation; medical devices; diagnostic reagent preservation; food preservation, such as plastic or paper food wrap; food, beverage, and industrial process pasteurizers; toilet bowls; recreational water; pools; and spas.

Preferably, the microbicidal compositions of the present invention are used to inhibit the growth of microorganisms at a locus selected from one or more of mineral slurries, pulp and paper processing fluids and additives, starch, emulsions, dispersions, paints, latices, coatings, construction adhesives, such as ceramic adhesives, carpet backing adhesives, photographic chemicals, printing fluids, household products such as bathroom and kitchen cleaners, cosmetics, toiletries, shampoos, soaps, detergents, industrial cleaners, floor polishes, laundry rinse water, metal working fluids, textile products, wood and wood products, agriculture adjuvant preservation, surfactant preservation, diagnostic reagent preservation, food preservation, and food, beverage, and industrial process pasteurizers.

The specific amount of the composition of this invention necessary to inhibit or control the growth of microorganisms and higher aquatic life forms in a locus depends upon the particular locus to be protected. Typically, the amount of the composition of the present invention to control the growth of microorganisms in a locus is sufficient if it provides from 0.1 to 1,000 ppm of the isothiazoline ingredient of the composition in the locus. It is preferred that the isothiazolone ingredients of the composition be present in the locus in an amount of at least 0.5 ppm, more preferably at least 4 ppm and most preferably at least 10 ppm. It is preferred that the isothiazolone ingredients of the composition be present in the locus in an amount of no more than 1000 ppm, more preferably no more than 500 ppm, and most preferably no more than 200 ppm.

EXAMPLES Materials and Methods

The synergism of the combination of the present invention was demonstrated by testing a wide range of concentrations and ratios of the compounds.

One measure of synergism is the industrially accepted method described by Kull, F. C.; Eisman, P. C.; Sylwestrowicz, H. D. and Mayer, R. L., in Applied Microbiology 9:538-541 (1961), using the ratio determined by the formula: Q _(a) /Q _(A) +Q _(b) /Q _(B)=Synergy Index(“SI”) wherein:

-   -   Q_(A)=concentration of compound A (first component) in ppm,         acting alone, which produced an end point (MIC of Compound A).     -   Q_(a)=concentration of compound A in ppm, in the mixture, which         produced an end point.     -   Q_(B)=concentration of compound B (second component) in ppm,         acting alone, which produced an end point (MIC of Compound B).     -   Q_(b)=concentration of compound B in ppm, in the mixture, which         produced an end point.

When the sum of Q_(a)/Q_(A) and Q_(b)/Q_(B) is greater than one, antagonism is indicated. When the sum is equal to one, additivity is indicated, and when less than one, synergism is demonstrated. The lower the SI, the greater the synergy shown by that particular mixture. The minimum inhibitory concentration (MIC) of a microbicide is the lowest concentration tested under a specific set of conditions that prevents the growth of added microorganisms.

Synergy tests were conducted using standard microtiter plate assays with media designed for optimal growth of the test microorganism. Minimal salt medium supplemented with 0.2% glucose and 0.1% yeast extract (M9GY medium) was used for testing bacteria; Potato Dextrose Broth (PDB medium) was used for testing yeast and mold. In this method, a wide range of combinations of microbicides was tested by conducting high resolution MIC assays in the presence of various concentrations of MBIT. High resolution MICs were determined by adding varying amounts of microbicide to one column of a microtitre plate and doing subsequent ten-fold dilutions using an automated liquid handling system to obtain a series of endpoints ranging from 2 ppm to 10,000 ppm active ingredient.

The synergy of the combinations of the present invention was determined against a bacterium, Escherichia coli (E. coli—ATCC #8739), a yeast, Candida albicans (C. albicans—ATCC 10231), and a mold, Aspergillus niger (A. niger—ATCC 16404). The bacteria were used at a concentration of about 5×10⁶ bacteria per mL and the yeast and mold at 5×10⁵ fungi per mL. These microorganisms are representative of natural contaminants in many consumer and industrial applications. The plates were visually evaluated for microbial growth (turbidity) to determine the MIC after various incubation times at 25° C. (yeast and mold) or 30° C. (bacteria).

The test results for demonstration of synergy of the MBIT combinations of the present invention are shown below in Tables 1 through 6. In each test, Second Component (B) was MBIT and the First Component (A) was the other commercial microbicide. Each table shows the specific combinations of MBIT and the other component; results against the microorganisms tested with incubation times; the end-point activity in ppm measured by the MIC for MBIT alone (Q_(B)), for the other component alone (Q_(A)), for MBIT in the mixture (Q_(b)) and for the other component in the mixture (Q_(a)); the calculated SI value; and the range of synergistic ratios for each combination tested (other component/MBIT or A/B).

TABLE 1 Contact Test Organisms Time Ca Cb S.I. Ca:Cb A. niger 3 days 1.275 — — — ATCC # 16404 — 150 — — 0.6 75 0.97 1:125.0000 0.9 75 1.21 1:83.3333  0.9 1.2 0.71 1:1.3333  1.275 1.2 1.01 1:0.9412  C. albicans 48 hrs 1.275 — — — ATCC # 10231 — 30 — — 1.275 1.86 1.06 1:1.4588  1.275 0.94 1.03 1:0.7373  72 hrs 1.275 — — — — 30 — — 1.275 1.86 1.06 1:1.4588  1.275 0.94 1.03 1:0.7373  Ps. aeruginosa 24 hrs 1.275 — — — ATCC#9027 — 100 — — 1.275 6 1.06 1:4.7059  48 hrs 1.275 — — — — 175 — — 0.6 100 1.04 1:166.6667 S. aureus 48 hrs 0.9 — — — ATCC#6538 — 60 — — 0.2625 30 0.79 1:114.2857 0.33 30 0.87 1:90.9091  0.6 30 1.17 1:50.0000  Ca—ppm AI of CMI/MI (Chloro-2-methyl-4-isothiazolin-3-one/2-Methyl-4-isothiazolin-3-one) Cb—ppm AI of MBIT (N-methyl-1,2-benzisothiazolin-3-one) Ratio: Ca:Cb

TABLE 2 Contact Test Organisms Time Ca Cb S.I. Ca:Cb A. niger 3 days 42.5 — — — ATCC # 16404 — 9.4 — — 4.25 4.7 0.60 1:1.1059 5.25 4.7 0.62 1:0.8952 8.75 4.7 0.71 1:0.5371 11 4.7 0.76 1:0.4273 20 4.7 0.97 1:0.2350 30 4.7 1.21 1:0.1567 4.25 2.4 0.36 1:0.5647 5.25 2.4 0.38 1:0.4571 8.75 2.4 0.46 1:0.2743 11 2.4 0.51 1:0.2182 20 2.4 0.73 1:0.1200 30 2.4 0.96 1:0.0800 42.5 2.4 1.26 1:0.0565 4.25 1.2 0.23 1:0.2824 5.25 1.2 0.25 1:0.2286 8.75 1.2 0.33 1:0.1371 11 1.2 0.39 1:0.1091 20 1.2 0.60 1:0.0600 30 1.2 0.83 1:0.0400 42.5 1.2 1.13 1:0.0282 7 days 200 — — — — 18.8 — — 42.5 9.4 0.71 1:0.2212 52.5 9.4 0.76 1:0.1790 65 9.4 0.83 1:0.1446 87.5 9.4 0.94 1:0.1074 110 9.4 1.05 1:0.0855 87.5 4.7 0.69 1:0.0537 110 4.7 0.80 1:0.0427 200 4.7 1.25 1:0.0235 65 2.4 0.45 1:0.0369 87.5 2.4 0.57 1:0.0274 110 2.4 0.68 1:0.0218 200 2.4 1.13 1:0.0120 87.5 1.2 0.50 1:0.0137 110 1.2 0.61 1:0.0109 200 1.2 1.06 1:0.0060 C. albicans 48 hrs 44 — — — ATCC # 10231 — 30 — — 2.6 15 0.56 1:5.7692 4.4 15 0.60 1:3.4091 8 15 0.68 1:1.8750 12 15 0.77 1:1.2500 17 15 0.89 1:0.8824 21 15 0.98 1:0.7143 26 15 1.09 1:0.5769 8 7.5 0.43 1:0.9375 12 7.5 0.52 1:0.6250 17 7.5 0.64 1:0.4412 21 7.5 0.73 1:0.3571 26 7.5 0.84 1:0.2885 44 7.5 1.13 1:0.1705 44 3.75 1.06 1:0.0852 35 1.86 0.86 1:0.0531 44 1.86 1.03 1:0.0423 44 0.94 1.03 1:0.0214 72 hrs >44 — — 30 — — 4.4 15 0.6 1:3.4091 8 15 0.68 1:1.8750 12 15 0.77 1:1.2500 17 15 0.89 1:0.8824 21 15 0.98 1:0.7143 26 15 1.09 1:0.5769 8 7.5 0.43 1:0.9375 12 7.5 0.52 1:0.6250 17 7.5 0.64 1:0.4412 21 7.5 0.73 1:0.3571 26 7.5 0.84 1:0.2885 44 7.5 1.25 1:0.1705 35 1.86 0.86 1:0.0531 44 1.86 1.06 1:0.0423 44 0.94 1.03 1:0.0214 Ps. Aeruginosa 24 hrs 4.25 — — ATCC#9027 100 — — 2 50 0.97  1:25.0000 3 50 1.21  1:16.6667 3 25 0.96 1:8.3333 4.25 25 1.25 1:5.8824 4.25 6 1.06 1:1.4118 48 hrs 5.25 — — — — 175 — — 0.875 100 0.74  1:114.2857 1.1 100 0.78  1:90.9091 2 100 0.95  1:50.0000 3 100 1.14  1:33.3333 5.25 12 1.07 1:2.2857 S. aureus 48 hrs 8.5 — — ATCC#6538 60 — — 1.05 30 0.62  1:28.5714 4 30 0.97 1:7.5000 6 30 1.21 1:5.0000 4 15 0.72 1:3.7500 6 15 0.96 1:2.5000 8.5 15 1.25 1:1.7647 6 2 0.74 1:0.3333 8.5 2 1.03 1:0.2353 6 1 0.72 1:0.1667 8.5 1 1.02 1:0.1176 Ca—ppm AI of DBNPA (2,2-Dibromo-3-nitrilopropionamide) Cb—ppm AI of MBIT(N-methyl-1,2-benzisothiazolin-3-one) Ratio: Ca:Cb

TABLE 3 Test Contact Organisms Time Ca Cb S.I. Ca:Cb A. niger 3 days 200 — — — ATCC # 16404 — 75 — — 2 37.5 0.51  1:18.7500 5.25 37.5 0.53 1:7.1429 8.75 37.5 0.54 1:4.2857 11 37.5 0.56 1:3.4091 20 37.5 0.60 1:1.8750 30 37.5 0.65 1:1.2500 42.5 37.5 0.71 1:0.8824 52.5 37.5 0.76 1:0.7143 65 37.5 0.83 1:0.5769 87.5 37.5 0.94 1:0.4286 110 37.5 1.05 1:0.3409 42.5 18.8 0.46 1:0.4424 52.5 18.8 0.51 1:0.3581 65 18.8 0.58 1:0.2892 87.5 18.8 0.69 1:0.2149 110 18.8 0.80 1:0.1709 200 18.8 1.25 1:0.0940 65 9.4 0.45 1:0.1446 87.5 9.4 0.56 1:0.1074 110 9.4 0.68 1:0.0855 200 9.4 1.13 1:0.0470 87.5 4.7 0.50 1:0.0537 110 4.7 0.61 1:0.0427 200 4.7 1.06 1:0.0235 110 2.4 0.58 1:0.0218 200 2.4 1.03 1:0.0120 200 1.2 1.02 1:0.0060 7 days 425 — — — — 150 — — 65 75 0.65 1:1.1538 87.5 75 0.71 1:0.8571 110 75 0.76 1:0.6818 200 75 0.97 1:0.3750 300 75 1.21 1:0.2500 300 37.5 0.96 1:0.1250 425 37.5 1.25 1:0.0882 200 18.8 0.6 1:0.0940 300 18.8 0.83 1:0.0627 425 18.8 1.13 1:0.0442 425 9.4 1.06 1:0.0221 425 4.7 1.03 1:0.0111 300 2.4 0.72 1:0.0080 425 2.4 1.02 1:0.0056 300 1.2 0.71 1:0.0040 425 1.2 1.01 1:0.0028 C. albicans 48 hrs 425 — — — ATCC # 10231 — 30 — — 87.5 15 0.71 1:0.1714 110 15 0.76 1:0.1364 200 15 0.97 1:0.0750 300 15 1.21 1:0.0500 875 7.5 2.31 1:0.0086 300 3.75 0.83 1:0.0125 425 3.75 1.13 1:0.0088 300 1.86 0.77 1:0.0062 425 1.86 1.06 1:0.0044 425 0.94 1.03 1:0.0022 72 hrs 525 — — — — 30 — — 110 15 0.71 1:0.1364 200 15 0.88 1:0.0750 300 15 1.07 1:0.0500 300 3.75 0.70 1:0.0125 425 3.75 0.93 1:0.0088 525 3.75 1.13 1:0.0071 425 1.86 0.87 1:0.0044 525 1.86 1.06 1:0.0035 425 0.94 0.84 1:0.0022 525 0.94 1.03 1:0.0018 Ps. aeruginosa 24 hrs 15 — — — ATCC#9027 — 100 — — 15 6 1.06 1:0.4000 48 hrs 26.25 — — — — 175 — — 10 100 0.95  1:10.0000 15 100 1.14 1:6.6667 15 50 0.86 1:3.3333 21.25 50 1.10 1:2.3529 21.25 25 0.95 1:1.1765 26.25 25 1.14 1:0.9524 21.25 12 0.88 1:0.5647 26.25 12 1.07 1:0.4571 21.25 6 0.84 1:0.2824 26.25 6 1.03 1:0.2286 S. aureus 24 hrs 30 — — — ATCC#6538 — 60 — — 3 30 0.60  1:10.0000 5.25 30 0.68 1:5.7143 11 30 0.87 1:2.7273 20 30 1.17 1:1.5000 20 15 0.92 1:0.7500 30 15 1.25 1:0.5000 30 3 1.05 1:0.1000 30 2 1.03 1:0.0667 30 1 1.02 1:0.0333 48 hrs 30 — — — — 60 — — 5.25 30 0.68 1:5.7143 11 30 0.87 1:2.7273 20 30 1.17 1:1.5000 20 15 0.92 1:0.7500 30 3 1.05 1:0.1000 30 2 1.03 1:0.0667 30 1 1.02 1:0.0333 Ca—ppm AI of HCHO (Formaldehyde) Cb—ppm AI of MBIT(N-methyl-1,2-benzisothiazolin-3-one) Ratio: Ca:Cb

TABLE 4 Test Contact Organisms Time Ca Cb S.I. Ca:Cb A. niger 3 days 0.65 — — — ATCC # 16404 — 75 — — 0.0425 37.5 0.57  1:882.3529 0.065 37.5 0.60  1:576.9231 0.11 37.5 0.67  1:340.9091 0.2 37.5 0.81  1:187.5000 0.3 37.5 0.96  1:125.0000 0.425 37.5 1.15  1:88.2353 0.525 18.8 1.06  1:35.8095 0.525 9.4 0.93  1:17.9048 0.65 9.4 1.13  1:14.4615 0.525 4.7 0.87 1:8.9524 0.65 4.7 1.06 1:7.2308 0.65 2.4 1.03 1:3.6923 0.65 1.2 1.02 1:1.8462 7 days 8.75 — — — — 150 — — 0.525 150 1.06  1:285.7143 1.1 75 0.63  1:68.1818 2 75 0.73  1:37.5000 3 75 0.84  1:25.0000 4.25 75 0.99  1:17.6471 5.25 75 1.10  1:14.2857 2 37.5 0.48  1:18.7500 3 37.5 0.59  1:12.5000 4.25 37.5 0.74 1:8.8235 5.25 37.5 0.85 1:7.1429 6.5 37.5 0.99 1:5.7692 8.75 37.5 1.25 1:4.2857 0.875 18.8 0.23  1:21.4857 1.1 18.8 0.25  1:17.0909 2 18.8 0.35 1:9.4000 3 18.8 0.47 1:6.2667 4.25 18.8 0.61 1:4.4235 6.5 18.8 0.87 1:2.8923 8.75 18.8 1.13 1:2.1486 2 9.4 0.29 1:4.7000 3 9.4 0.41 1:3.1333 4.25 9.4 0.55 1:2.2118 5.25 9.4 0.66 1:1.7905 6.5 9.4 0.81 1:1.4462 8.75 9.4 1.06 1:1.0743 2 4.7 0.26 1:2.3500 3 4.7 0.37 1:1.5667 4.25 4.7 0.52 1:1.1059 5.25 4.7 0.63 1:0.8952 6.5 4.7 0.77 1:0.7231 8.75 4.7 1.03 1:0.5371 5.25 2.4 0.62 1:0.4571 6.5 2.4 0.76 1:0.3692 8.75 2.4 1.02 1:0.2743 5.25 1.2 0.61 1:0.2286 6.5 1.2 0.75 1:0.1846 8.75 1.2 1.01 1:0.1371 C. albicans 48 hrs 3.25 — — ATCC # 10231 — 30 — — 2.625 7.5 1.06 1:2.8571 2.625 3.75 0.93 1:1.4286 3.25 3.75 1.13 1:1.1538 3.25 1.86 1.06 1:0.5723 3.25 0.94 1.03 1:0.2892 72 hrs 3.25 — — — — 30 — — 3.25 1.86 1.06 1:0.5723 3.25 0.94 1.03 1:0.2892 Ps. aeruginosa 24 hrs 650 — — — ATCC#9027 — 100 — — 525 25 1.06 1:0.0476 525 12 0.93 1:0.0229 650 12 1.12 1:0.0185 650 6 1.06 1:0.0092 48 hrs 650 — — — — 175 — — 200 100 0.88 1:0.5000 300 100 1.03 1:0.3333 525 50 1.09 1:0.0952 525 25 0.95 1:0.0476 650 25 1.14 1:0.0385 650 12 1.07 1:0.0185 650 6 1.03 1:0.0092 S. aureus 24 hrs 30 — — — ATCC#6538 — 30 — — 3 15 0.60 1:5.0000 5.25 15 0.68 1:2.8571 6.5 15 0.72 1:2.3077 8.75 15 0.79 1:1.7143 11 15 0.87 1:1.3636 20 15 1.17 1:0.7500 20 7.5 0.92 1:0.3750 30 7.5 1.25 1:0.2500 30 2 1.07 1:0.0667 30 1 1.03 1:0.0333 48 hrs 200 — — — — 60 — — 0.2 30 0.50  1:150.0000 2 30 0.51  1:15.0000 20 30 0.60 1:1.5000 30 30 0.65 1:1.0000 42.5 30 0.71 1:0.7059 52.5 30 0.76 1:0.5714 87.5 30 0.94 1:0.3429 110 30 1.05 1:0.2727 4.25 15 0.27 1:3.5294 2 15 0.26 1:7.5000 20 15 0.35 1:0.7500 30 15 0.40 1:0.5000 42.5 15 0.46 1:0.3529 52.5 15 0.51 1:0.2857 87.5 15 0.69 1:0.1714 110 15 0.80 1:0.1364 200 15 1.25 1:0.0750 20 7.5 0.23 1:0.3750 30 7.5 0.28 1:0.2500 42.5 7.5 0.34 1:0.1765 52.5 7.5 0.39 1:0.1429 87.5 7.5 0.56 1:0.0857 110 7.5 0.68 1:0.0682 200 7.5 1.13 1:0.0375 87.5 3 0.49 1:0.0343 110 3 0.6 1:0.0273 200 3 1.05 1:0.0150 200 2 1.03 1:0.0100 200 1 1.02 1:0.0050 Ca—ppm AI of OIT (2-N-octyl-4-isothiazolin-3-one) Cb—ppm AI of MBIT(N-methyl-1,2-benzisothiazolin-3-one) Ratio: Ca:Cb

TABLE 5 Test Contact Organisms Time Ca Cb S.I. Ca:Cb A. niger 3 days 52.5 — — — ATCC # 16404 — 37.5 — — 6.5 18.8 0.63 1:2.8923 11 18.8 0.71 1:1.7091 20 18.8 0.88 1:0.9400 30 18.8 1.07 1:0.6267 52.5 2.4 1.06 1:0.0457 52.5 1.2 1.03 1:0.0229 7 days 87.5 — — — — 150 — — 11 75 0.63 1:6.8182 20 75 0.73 1:3.7500 30 75 0.84 1:2.5000 42.5 75 0.99 1:1.7647 52.5 75 1.10 1:1.4286 42.5 37.5 0.74 1:0.8824 52.5 37.5 0.85 1:0.7143 65 37.5 0.99 1:0.5769 52.5 18.8 0.73 1:0.3581 65 18.8 0.87 1:0.2892 87.5 18.8 1.13 1:0.2149 87.5 9.6 1.06 1:0.1097 87.5 4.7 1.03 1:0.0537 87.5 2.4 1.02 1:0.0274 87.5 1.2 1.01 1:0.0137 C. albicans 48 hrs 525 — — — ATCC # 10231 — 30 — — 8.75 15 0.52 1:1.7143 20 15 0.54 1:0.7500 42.5 15 0.58 1:0.3529 65 15 0.62 1:0.2308 110 15 0.71 1:0.1364 200 15 0.88 1:0.0750 300 15 1.07 1:0.0500 65 7.5 0.37 1:0.1154 110 7.5 0.46 1:0.0682 200 7.5 0.63 1:0.0375 300 7.5 0.82 1:0.0250 425 7.5 1.06 1:0.0176 200 3.75 0.51 1:0.0188 300 3.75 0.70 1:0.0125 425 3.75 0.93 1:0.0088 525 3.75 1.13 1:0.0071 200 1.86 0.44 1:0.0093 300 1.86 0.63 1:0.0062 425 1.86 0.87 1:0.0044 525 1.86 1.06 1:0.0035 425 0.94 0.84 1:0.0022 525 0.94 1.03 1:0.0018 72 hrs 525 — — — — 30 — — 8.75 15 0.52 1:1.7143 20 15 0.54 1:0.7500 42.5 15 0.58 1:0.3529 65 15 0.62 1:0.2308 110 15 0.71 1:0.1364 200 15 0.88 1:0.0750 300 15 1.07 1:0.0500 65 7.5 0.37 1:0.1154 110 7.5 0.46 1:0.0682 200 7.5 0.63 1:0.0375 300 7.5 0.82 1:0.0250 425 7.5 1.06 1:0.0176 200 3.75 0.51 1:0.0188 300 3.75 0.70 1:0.0125 425 3.75 0.93 1:0.0088 525 3.75 1.13 1:0.0071 200 1.86 0.44 1:0.0093 300 1.86 0.63 1:0.0062 425 1.86 0.87 1:0.0044 525 1.86 1.06 1:0.0035 425 0.94 0.84 1:0.0022 525 0.94 1.03 1:0.0018 Ps. Aeruginosa 24 hrs 875 — — — ATCC#9027 — 100 — — 650 25 0.99 1:0.0385 875 6 1.06 1:0.0069 48 hrs 875 — — — — 175 — — 875 12 1.07 1:0.0137 875 6 1.03 1:0.0069 S. aureus 24 hrs 1100 — — — ATCC#6538 — 30 — — 200 15 0.68 1:0.0750 300 15 0.77 1:0.0500 425 15 0.89 1:0.0353 525 15 0.98 1:0.0286 650 15 1.09 1:0.0231 875 7.5 1.05 1:0.0086 875 3 0.90 1:0.0034 1100 3 1.1 1:0.0027 1100 2 1.07 1:0.0018 1100 1 1.03 1:0.0009 48 hrs 1100 — — — — 60 — — 200 15 0.43 1:0.0750 300 15 0.52 1:0.0500 425 15 0.64 1:0.0353 525 15 0.73 1:0.0286 650 15 0.84 1:0.0231 875 15 1.05 1:0.0171 875 7.5 0.92 1:0.0086 1100 7.5 1.13 1:0.0068 875 3 0.85 1:0.0034 1100 3 1.05 1:0.0027 1100 2 1.03 1:0.0018 1100 1 1.02 1:0.0009 Ca—ppm AI of Propiconazole (1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole) Cb—ppm AI of MBIT(N-methyl-1,2-benzisothiazolin-3-one Ratio: Ca:Cb

TABLE 6 Test Contact Organisms Time Ca Cb S.I. Ca:Cb A. niger 3 days 4.25 — — — ATCC # 16404 — 37.5 — — 1.1 18.8 0.76  1:17.0909 2 18.8 0.97 1:9.4000 7 days 11 — — — — 150 — — 11 2.4 1.02 1:0.2182 11 1.2 1.01 1:0.1091 C. albicans 48 hrs 110 — — — ATCC # 10231 — 30 — — 42.5 15 0.89 1:0.3529 52.5 15 0.98 1:0.2857 65 15 1.09 1:0.2308 87.5 7.5 1.05 1:0.0857 110 1.86 1.06 1:0.0169 110 0.94 1.03 1:0.0085 72 hrs 110 — — — — 30 — — 42.5 15 0.89 1:0.3529 52.5 15 0.98 1:0.2857 65 15 1.09 1:0.2308 87.5 7.5 1.05 1:0.0857 110 1.86 1.06 1:0.0169 110 0.94 1.03 1:0.0085 Ps. aeruginosa 24 hrs 875 — — — ATCC#9027 — 100 — — 650 25 0.99 1:0.0385 875 6 1.06 1:0.0069 48 hrs 1100 — — — — 175 — — 875 50 1.08 1:0.0571 875 25 0.94 1:0.0286 1100 25 1.14 1:0.0227 1100 12 1.07 1:0.0109 1100 6 1.03 1:0.0055 S. aureus 24 hrs 300 — — — ATCC#6538 — 30 — — 87.5 15 0.79 1:0.1714 110 15 0.87 1:0.1364 200 15 1.17 1:0.0750 200 7.5 0.92 1:0.0375 300 7.5 1.25 1:0.0250 200 3 0.77 1:0.0150 200 2 0.73 1:0.0100 300 2 1.07 1:0.0067 200 1 0.70 1:0.0050 300 1 1.03 1:0.0033 48 hrs 425 — — — — 60 — — 0.65 30 0.50  1:46.1538 2 30 0.50  1:15.0000 4.25 30 0.51 1:7.0588 6.5 30 0.52 1:4.6154 11 30 0.53 1:2.7273 20 30 0.55 1:1.5000 30 30 0.57 1:1.0000 42.5 30 0.60 1:0.7059 52.5 30 0.62 1:0.5714 65 30 0.65 1:0.4615 87.5 30 0.71 1:0.3429 110 30 0.76 1:0.2727 200 30 0.97 1:0.1500 300 30 1.21 1:0.1000 87.5 15 0.46 1:0.1714 110 15 0.51 1:0.1364 200 15 0.72 1:0.0750 300 15 0.96 1:0.0500 425 15 1.25 1:0.0353 200 7.5 0.6 1:0.0375 300 7.5 0.83 1:0.0250 425 7.5 1.13 1:0.0176 200 3 0.52 1:0.0150 300 3 0.76 1:0.0100 425 3 1.05 1:0.0071 200 2 0.5 1:0.0100 300 2 0.74 1:0.0067 425 2 1.03 1:0.0047 200 1 0.49 1:0.0050 300 1 0.72 1:0.0033 425 1 1.02 1:0.0024 Ca—ppm AI of Tebuconazole (alpha-[2-(4-chlorophenylethyl]-alpha-(1,1-dimethylethyl)- 1H- 1,2,4-triazole-1-ethanol) Cb—ppm AI of MBIT (N-methyl-1,2-benzisothiazolin-3-one) Ratio: Ca:Cb 

The invention claimed is:
 1. A microbicidal composition comprising: (a) N-methyl-1,2-benzisothiazolin-3-one; and (b) 2-N-octyl-4-isothiazolin-3-one; and a ratio of 2-N-octyl-4-isothiazolin-3-one to N-methyl-1,2-benzisothiazolin-3-one is from 1:0.0273 to 1:882; wherein the microbicidal composition is synergistic. 